1. Field of the Invention
The present invention relates to an ink jet head and an ink jet head apparatus having the ink jet head. Furthermore, the present invention relates to a method of and an apparatus for manufacturing the ink jet head, and more particularly, to the alignment in manufacture of energy generating elements employed for discharge in the head.
2. Description of the Related Art
FIGS. 1 and 2 show an example of a conventional ink jet head. FIG. 1 is a longitudinal cross-sectional view partially showing a surface of a head which is cut horizontally along a discharge port row. FIG. 2 is a cross-section taken along the line 2-2' of FIG. 1.
As shown in FIG. 1, a plurality of discharge ports 1101 are provided in a conventional ink jet head. An electro-thermal transducer for generating thermal energy utilized to discharge a liquid (hereinafter referred to as an ink) from the discharge port 1101 is provided for every ink flow passage 1108. Each of the electro-thermal transducers 1103 is mainly constituted by a heating resistor 1102 and electrode interconnections 1110 for supplying power to the heating resistor 1102.
More specifically, as shown in FIG. 2, an insulator film 1111 and an interlayer film 1112 are formed on a substrate 103 made of, for example, silicon, and a heating resistor layer 1102 having a pattern such as that shown in FIG. 1 is formed on these films. Patterned electrode interconnections 1110 made of, for example, Al are formed on a portion of the heating resistor layer 1102. The portion of the heating resistor layer 1102 on which no electrode interconnections are formed constitutes a heating portion 1116.
Furthermore, a first protective film 1113 and a second protective film 1114 are coated on the patterned heating resistor layer 1102 and the electrode interconnection 1110. A heater board 104 (see FIG. 2) is constituted by the substrate 103, the electro-thermal transducers formed on the substrate 103 and so on.
Referring to FIG. 1, the ink flow passages 1108 are partitioned by flow passage walls 1109. The end portions of the ink flow passages 1108 remote from the discharge ports 1101 communicate with a common liquid chamber 1106. The common liquid chamber 1106 stores the ink supplied from an ink tank (not shown). The ink supplied from the common liquid chamber 1106 is introduced to each of the ink flow passages 1108 where it is retained by virtue of the meniscus formed near the discharge port 1101. At that time, if the electro-thermal transducer 1103 is selectively driven, film boiling occurs in the ink as a result of the thermal energy generated by the electro-thermal transducer 1103, generating a bubble and in turn, ejecting ink. The ink is discharged from the discharge port 1101 by virtue of the growth of the bubble.
A ceiling plate 105 made of, for example, a resin is joined onto the heater board 104 of the ink jet head.
More specifically, the ceiling plate 105 is a unit in which an orifice plate 1104 having the discharge ports 1101 formed therein is integrally formed with the flow passage walls 1109. The ceiling plate 105 is joined to the heater board 104 in the manner described below: as shown in FIG. 2, the ceiling plate 105 is placed while aligning the discharge port forming portion of the ceiling plate 105 relative to the electro-thermal transducers on the heater board 104 by means of, for example, the image processing, and a rear portion of the ceiling plate 105 (remote from the discharge port forming portion) is then temporarily fixed by, for example, an adhesive. Thereafter, the flow passage walls are pressed by an elastic member (not shown), such as a plate spring, from above, whereby the adjacent electro-thermal transducers 1103 on the heater board 104 are separated from each other by the flow passage walls 1109 in such a manner that a single electro-thermal transducer 1103 is disposed in every ink flow passage 1108.
However, in the conventional heater board structure described above, since the lower end of the flow passage wall 1109 of the ceiling plate 105 is brought into contact with a flow passage wall joining surface 1115 forming a convex portion on the heater board 104, if a small gap is created between the flow passage wall 1109 and the joining surface 1115, the ink pressure waves generated by bubbling may propagate to the adjoining ink flow passages, transferring the bubbling energy to the adjacent ink flow passages. This makes ink discharge unstable. Particularly, this becomes a serious problem in a case where the electro-thermal transducers 1103 and the flow passage walls 1109 are provided close to each other as a consequence of an increase in the resolution of the ink jet head.
Further, in the above structure in which the heater board 104 and the ceiling plate 105 are closely attached to each other by means of the elastic member, such as a plate spring, without using an adhesive, the direction in which the fixing force is applied may vary or the positioning accuracy may deteriorate, thus generating a positional deviation between the ceiling plate 105 and the heater board 103. In that case, in the above-described structure in which the flow passage walls 1109 are brought into contact with the convex portions on the heater board 104, even if the above gap is very small, a portion of the flow passage wall 1109 may rise above the convex portion or the flow passage wall 1109 may rise on the electro-thermal transducer 1103. In these cases, unstable bubbling, transfer of the bubbling energy into the adjacent ink flow passages or crosstalk may occur, making the dot diameter non-uniform or degrading the recording quality.